1. Field of the Invention
The present invention relates to an apparatus for manufacturing curved sheets of glass with upper and lower molds, and more particularly to a mold changer carriage for changing such upper and lower molds altogether.
2. Description of the Relevant Art
Curved sheets of glass for use as automobile windshields, for example, are manufactured by an apparatus as disclosed in Japanese Patent Publication No. 53-12931, for example. The disclosed manufacturing apparatus has a heating furnace for heating a sheet of glass up to a temperature near its softening point. The heated glass sheet is delivered horizontally to a position between upper and lower molds of a shaping device by feed rollers. The glass sheet is then positioned between the upper and lower molds, and the lower mold is lifted above the feed rollers to place the glass sheet on the lower mold. Thereafter, the upper mold is lowered into pressing contact with the glass sheet on the lower mold for curving the glass sheet to a desired curved shape.
For manufacturing a differently curved glass sheet, the upper and lower molds in the shaping device are replaced with another set of upper and lower molds. The process of removing the existing molds from the shaping assembly and replacing them with new molds is however very complex and time-consuming. More specifically, the upper and lower molds are fixedly mounted on attachment plates fixed to lifting/lowering devices or hydraulic cylinders. In order to replace the upper and lower molds with new ones, they are detached from the respective attachment plates and delivered to a given storage area for storage. Then, a new upper mold stored in another storage area is carried into the shaping device, and lifted and attached to the attachment plate therefor, and a new lower mold is similarly delivered from the storage area into the shaping device and attached to the corresponding attachment plate. Thereafter, the upper and lower molds are registered with each other.
Japanese Laid-Open Patent Publication No. 62-182124 discloses a mold changer for use with an apparatus for manufacturing curved sheets of glass. The disclosed mold changer includes a carrier plate having a number of steel balls on its upper surface. Upper and lower attachment plates which are interconnected by positioning rods are placed on the carrier plate, the upper and lower attachment plates supporting upper and lower molds, respectively. By moving the carrier plate along rails, the upper and lower molds can simultaneously be moved between a shaping device and their storage location. Problems with this mold changer are that a wide floor space is needed for the installation of the rails, the mold changer itself tends to interfere with various other operations, and when large molds are to be replaced or used, considerably large forces are required to move the molds.